Preparation of compounds containing silicon and boron



United States Patent PREPARATION OF COMPOUNDS CONTAINING SILICON AND BORON Stephen J. Groszo s, Darien, Conn., assignor to American Cyanamid 'Company,,New York, N.Y., a corporation of Maine Application September 24, 1957 Serial No. 685,826

7 Claims, (Cl. 260-4482) No Drawing.

This invention relates to the preparation of new chemical compounds and more particularly to the preparation of compounds containing boron and silicon. Still more siloxane substance containing an average of from 0.16 to 1.0 halogen atom per silicon atom. Krieble U.S.

Patent No. 2,440,101, dated April 20, 1948, discloses and claims tris-(trimethylsilyl) borate, the formula for Hz The compounds prepared by the method of this invention may be represented graphically by the following general formula:

wherein each R represents a radical of the class consisting of hydrocarbon and halohydrocarbon radicals, and

are the same or different. An illustrative example of a compound embraced by FormulaII is di-(triphenylsilyl)- phenylbororiate, which also properly may be designated as triphenylsilylphenylboronate, and the formula for which is The compounds produced by the method of the present invention should not be confused with the polymeric carbon-boronic acid, which polymeric reaction products are described in Upson Patent No. 2,517,945, dated August 8, 1950, as having as recurring structural units "where R, R and R are monovalent hydrocarbon radicals. Upson obtains his polymers by heating a mixture reaction products of a hydrocarbosilanediol and a hydroof a polyhydric organosilanol, for example, diphenylsilanediol, and a boronic acid, for example, benzeneboronic acid, under atmospheric pressure in a reaction vessel at a temperature sufiicient to melt the-reactants and to vaporize the water which isformed, preferably at 170 to 260 C. When the evolution of water subsides, the

I cyclopentyl,

2 resulting viscous molten polymer is heatedunder reduced pressure to remove any water vapor or other volatile products remaining in the mixture. The polymer is then allowed to cool to room-temperature. QUpsonalso states that Modifying agents such as monohydric organosilanols (R SiOH) and boronic [borinic] acids (R BOH) may be added to the reactants either at the start or at any stage of the reaction. These agents act to terminate polymer chains and are accordingly usefulin controlling the molecular weight of the polymers.

Illustrative examples of hydrocarbon radicals represented by R in Formula II are alkyl (including cycloalkyl), alkenyl (including cycloalkenyl), aralkyl, aralkenyl, aryl, alkaryl and alkenylaryl. More specific examples of such radicals are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, see-butyl, amyl, isoamyl, hexyl to octadecyl, inclusive (both normal and isomeric forms), cyclopentenyl, cyclohexyl, cyclohexenyl, cycloheptyl, etc.; benzyl, phenylethyl, phenylpropyl, phenylisopropyl, phenylallyl, etc.; phenyl, biphenylyl or xenyl, naphthyl, etc.; tolyl, xylyl, ethylphe'nyl, propylphenyl, isopropylphenyl, butylphenyl, allylphenyl, etc.; and vinyl, allyl, methallyl', propenyl, isopropenyl (betaallyl), l-butenyl, Z-butenyl (crotyl), 3-butenyl, pentenyl, hexenyl, butadienyl, etc. Illustrative examples of halohydrocarbon radicals represented by R in Formula II are the' halogen'ated (chlorinated, brominated, fluorinated and iodinated) radicals, including the 'perhalogenated radicals, corresponding to the hydrocarbon radicals mentioned above by way of example. Still other examples of hydrocarbon and halohydrocarbon radicals represented by R" in Formula II will be apparent to those skilled in the art from the foregoing illustrative examples.

The B,Si compounds (i.e., compounds containing boron and silicon) prepared. by the method of this invention range from liquids to semi-liquids and solidsin normal'state. Many of the compounds, more particularly those wherein R in Formula II represents a carbocyclic radical, have improved hydrolytic resistance and thermal resistance (often referred to as hydrolytic stability and thermal stability) as compared with most of the-prior organoboron compounds. The compounds produced by the method of the present invention are useful, for instance, as chemical intermediates in the preparation of organic materials containing both boronand silicon in the molecule. They can be employed in high-temperature applications, as modifiers of conventional polymeric ma terials, including synthetic resins, and "as neutron absorbers. They also are useful as components of flameresisting compositionst as plasticizers; as scintillation counters; as the active ingredient in insecticides, bactericides, germicides, fungicides, pesticides and the like; as a .component of arc-extinguishing tubes, and especially of surfaces that are exposed to the action of the are. Other uses include: as polymer additives to impart neutron-absorbing properties to the polymer-to which the compound of the invention is added and to improvethe thermal stability of the polymer; as heat-exchangemedia or as modifiers of such media whereby they can be used at higher temperatures; as petroleum additives which are hydrolytically stable, especially those embraced by Formula II wherein R is a carbocyclic radical (e. g.,' as'viscosity-index improvers, in lubricants and greases for hightemperature applications, as cetane improvers, ignition promoters, anti-knock agents, preventives of pre-ignition,

etc.) and in making new types of dyes and pigments.

In any-of the aforementioned and other applications or uses, one can employ a single compound of the kind embraced by Formula II or a pluralityof such-compounds in any proportions. They can be 'use'din'conjunction with any of the conventional components of Patented Dec; 1 1959 flame-resisting compositions, plasticizers, insecticides, bactericides, germicides, fungicides, pesticides, and other compositions hereinbefore mentioned by way of illustrating the fields of utility, generically and specifically, of the boronates of this invention.

The symmetrical compounds embraced by Formula II are prepared by reacting together (1) a 'boronic acid represented by the general formula where R has the same meaning as given above with reference to Formula II and (2) a silicon compound represented by the general formula wherein each R has the .same meaning as given above with reference to Formula II, and Y represents aradical of the class consisting of --OH and --NH radicals, the boronic acid (1) and the silicon compound of (2) being employed in a molar ratio of at least 2 moles of the latter per mole of the former; and isolating a compound represented by Formula II from'the resultingreaction mass.

Unsymmetrical compounds embraced by Formula II can be prepared, for example, by using a mixture of different starting reactants; that is, compounds wherein the hydrocarbon or halohydrocarbon substituents are diiier- .ent. Thus, one can react, for instance, one mole of phenylboronic acid with two moles of tri-(p-tolyl)silanol to produce di-(tri-p-tolylsilyl)phenylboronate; or one vmole of n-butylboronic acid with two moles of tri-(mchlorophenyl)silanol to produce di-(tri-m-chlorophenylsilyl)-n-butylboronate; or one mole of n-propylboronic acid with two moles of triethylsilanol to produce di-(triethylsilyl)-n propylboronate.

In order that those skilled in the art may better understand how the present invention can be carried into effect, the followingexamples are given by way of illustration and not by way of limitation. All parts and percentages are by weight unless otherwise indicated;

EXAMPLE 1 H ro.nt)tsion+ctnt-n on -3 otHmsFo-n-m-siwtmn CtHs .Intoa three-necked flask equipped with a stirrer and a condenser provided with a Dean and Stark trap are charged 27.23 g. (0.1 mole) triphenylsilanol (prepared .by hydrolysis of (C H SiCl), 6.09 g. (0.05 mole) phen- ;ylboronic acid and 75 ml. benzene. The reaction mixture is refluxed until 1.4 ml. water has azeotroped into the trap (theoretical water of reaction is 1.8 ml.). Benzene is then removed from the reaction mass until a filterable slurry remains. The solid fraction is filtered off and recrystallized from hexane to give white crystals, M.P. 132-133 C. Infrared analysis confirms the product as being di-(triphenylsilyl)phenylboronate. The total yield of recrystallized product is 71% of the theoretical, which corresponds to the percent (of the total) of water of reaction obtained.

ANALYSIS Calculated f0! (3421335138120: 79. 98 5. 5 Found I 78. 24 5. 59

I Sample is mixed with 0110 prior to combustion. b A rapid Q-I-H determination is used.

EXAMPLE 2 Di-(triphenylsilyl)n-butylboronate is prepared by essentially the same procedure described under Example 1 with the exception that 0.05 mole of n-butylboronic acid is used instead of 0.05 mole of phenylboronic acid. The total yield of recrystallized product is about 69% of the theoretical. Its structure is confirmed, by infrared analysis.

Instead of phenylboronic acid or n-butylboronic acid one can use any other hydrocarbonor halohydrocarbonboronic acid, e.g., the various halo-(i.e.,- chloro-, bromo-, fluoroand iodo-)phenylboronic acids, the various other aryl and halogenoarylboronic acids, for instance the o-, mand p-tolyl and halogenotolylboronic acids, the various xylyl and halogenoxylylboronic acids; the 'various aralkyl and nuclearly halogenated aralkylooronic acids, for instance benzylboronic acid, phenylethylboronic acid and the corresponding halogenated (nuclearly and/or sidechain halogenated) derivatives; other alltyl (including cycloalkyl)boronic acids, among which may be mentioned methyl-, ethyl-, propyl-, isopropyl-, isobuty1-, sec. butyl tert.-butyland amylthrough octadecylboronic acids, cyclopentyl-, cyclohexyland other cycloalkylboronic acids, the corresponding halogeno (including perhalogeno) derivatives; allyland other alkenylboronic acids; and others that will be apparent to those skilled in the art from the foregoing examples and from the definition of R in Formula H.

EXAMPLE 3 Di-(tri-m-chlorophenylsilyl)phenylboronate is obtained by following the method of Example 1 but using 0.1 mole of tri-(m-chlorophenyl)silanol instead of 0.1 mole of triphenylsilanol. The structure is confirmed by infrared analysis, and the total yield of recrystallized product is more than 65% of the theoretical.

EXAMPLE 4 (A) Preparation of triphenylsilylamine Triphenylsilylamine is prepared (using the method of Kraus and Rosen) by liquefying an excess of ammonia in a flask charged with 88.2 g. (0.3 mole) triphenylchlorosilane. After stirring for two hours at low temperatures, ca. -70 C., the reaction mixture is allowed to warm to room temperature. The light brown solid which remains after the excess ammonia has vaporized is then extracted for 2hours with petroleum ether, using a Soxhlet extractor. The resulting orange solution is heated with decolorizing carbon and filtered hot. On standing, 27.89 g. triphenylsilylamine crystallizes out of the light yellow solution. Concentration of the filtrate results in an additional crop of 13.53 g. of the colorless solid, MP. 53 -55 C. The total yield is 50% of the theoretical.

(B) Preparation of di-(triphenylsilyl)phenylboronate VIII (0,3,),81013 ostwum, NH;

A three-necked flask, equipped with a stirrer, nitrogeninlet and a Dean and Stark trap with a condenser and drying tube, are charged with 27.89 g. (0.101 mole) triphenylsilylamine, 6.09 g. (0.05 mole) phenylboronic acid and 75 ml. benzene. The reaction mixture is heated to reflux and after two hours at. reflux only a negligible amount of water has collected in the trap. Tests with HCl at the exit drying tube indicate the evolution of ammonia during the reaction. On cooling the concentrated benzene solution, a colorless crystalline solid is obtained. Infrared analysis of a recrystallized portion of the solid, M.P. 131.5 l33 C., confirms the identity of the product as. di-(triphenylsilyl)phenylboronate.

ANALYSIS Calculated tor OuHJsBShOg 79.98 5. 52 Found. 77. 90 1 5. 54

1 Mixed in a capsule with CuO.

Di-(triphenylsilyl)cyclohexylboronate is prepared by essentially the same procedure described under Example 4 with the exception that 0.05 mole of cyclohexylboronic acid is used instead of 0.05 mole of phenylboronic acid. The structure of the product is confirmed by infrared analysis. The total yield of the recrystallized product. is about 50% of the theoretical.

Cyclohexylboronic acid is prepared as follows:

Cyclohexyl magnesium bromide is prepared from 0.1 mole cyclohexylbromide and 0.1 gram atom magnesium turnings in ether solution in the usual manner. This solution is added dropwise over a period of 6 to 8 hours to a solution of 0.11 mole tri-n-butyl borate in 100 ml. dry ether maintained at a temperature of about -75 C. (Dry Ice-acetone bath). The reaction mixture is allowed to warm to about C. when 60 ml. of-10%, by volume, aqueous H 80 is added over a period of to minutes. The ether solution is separated, washed with water and extracted with three portions of 5% aqueous NaOH solution. The aqueous extract is acidified with 10% aqueous H 50 and the mixture is extracted with three 40 ml. portions of ether. The combined ether extracts are then evaporated (without the necessity of drying) on a water bath to yield cyclohexylboronic acid, one-half of which (i.e., 0.05 mole) can be used as described above without further purification.

EXAMPLE 6 Di-(tri-n-butylsilyl)n-butylboronate is made from 0.101 mole tri-n-butylsilylamine and 0.05 mole of n-butylboronic acid, following the same general procedure described under Example 4. Infrared analysis confirms the structure of the product, which is obtained in a fair yield.

EXAMPLE 7 This example illustrates the preparation of bis[(dicyclohexyl) phenylsilyl] butylboronate.

IX HnCo 11-04119 0111111 ucab @0131:

In the manner described inExample 1, 0.1 mole (dicyclohexyl)phenylsilanol (prepared according to the procedure of N. W. Cusa and F. S. Kipping, J. Chem. Soc., 1932, 2205), 0.05 mole n-butylboronic acid and 75 ml. toluene are charged into a three-necked flask. The mixture is refluxed until 1.7 ml. water has azeotroped. Toluene is then removed until a filterable slurry remains. On

6 cooling, the solid product is removed by filtration and recrystallized from n-hex'ane to give colorless crystals of bis[(dicyclohexyl)phenylsilyl]-n-butylboronate. Infrared analysis confirms the structure of the product.

EXAMPLE 9 In like manner to Example 8, 0.1 mole benzyl (dipheny1)silanol (prepared according to the procedure of H. Gilman, R. A. Benkeser and G. E. Dunn, J. Amer. Chem. Soc., 72, 1689 (1950)) is reacted with 0.05 mole phenylboronic acid to yield a colorless,'crystalline solid identified by infrared analysis as being bis[benzyl(diphenyl)- silyllphenylboronate.

EXAMPLE 10 Parts Polyvinyl chloride (gamma polyvinyl chloride) Di-(triphenylsilyl)phenylboronate 50 are mixed together on a standard rubber millat about C. until a sheet, 40 to 50 mils thick, is obtained. The resulting sheet is flexible, tough, somewhat elastic and has good tensile strength characteristics. It is suitable for uses where polyvinyl chloride compositions are now employed.

One can replace part of the di-(triphenylsilyl)phenylboronate used in the above formulation, for instance up to 90% by weight thereof (45 parts), with other plasticizers for polyvinyl chloride, e.g., a saturated aliphatic hydrocarbon triester of cyanuric acid, especially a trialkyl cyanurate and more particularly one containing not less than 4 and not more than 6 carbon atoms in each alkyl radical. The cyanuric triester not only functions as a plasticizer for polyvinyl chloride but also renders the plasticized composition resistant to discoloration under the action of heat.

The compounds prepared by the method of this invention can be used in plasticized polyvinyl halide (chloride, bromide, etc.) and polyvinylidene halide (chloride, bromide, etc.) compositions, alone or with other plasticizers or modifiers, in amounts corresponding to from 2% to 65% by weight of the plasticized composition.

Uses of the boron and silicon-containing compounds embraced by Formula II in more modern scientific applications have been mentioned hereinbefore.

In my copending application Serial No. 774,832, filed November 19, 1958, as a division of the aforementioned application Serial No. 685,826, filed September 24, 1957, claims are made to acompound represented by the general formula shown in Formula II and where each R shown in that formula represents an aryl, alkaryl or halogenoaryl radical, specifically di-(triphenylsilyl)phenylboronate, di-(tri-m-chlorophenylsilyl)phenylboronate and di(tri-p-tolylsilyl)m-chlorophenylboronate.

I claim:

1. The method of preparing a compound represented by the general formula wherein each R represents a radical of the class consisting of hydrocarbon and halohydrocarbon radicals, said method comprising reacting together (1) a boronic acid represented by the general formula wherein each R has the same meaning as given above, and Y represents a radical of the class consisting of OH and --NH radicals, the boronic acid of (1) and the silicon compound of (2) being employed in a molar ratio of at least 2 moles of the latter per mole of the former; and isolating a compound represented by the first-given formula from the resulting reaction mass.

2. A method as in claim 1 wherein each R represents the same radical of the class consisting of hydrocarbon and halohydrocarbon radicals.

3. A method as in claim 1 wherein Y represents an OH radical.

4. A method as in claim 1 wherein Y represents an -NH radical.

5. A method as in claim 1 wherein each R represents the same radical of the class consisting of hydrocarbon and halohydrocarbon radicals, and Y represents an OH radical.

6. A method as in claim 1 wherein each R represents the same radical of the class consisting of hydrocarbon and halohydrocarbon radicals, and Y represents an NH radical.

7. The method of preparing a compound represented by the general formula wherein each R represents a radical of the class consisting of hydrocarbon and halohydrocarbon radicals, each of the radicals represented by the Rs attached to each of the Si atoms being the same but being different from the radical represented by the R attached to the B atom, said method comprising reacting together (1) a boronic acid represented by the general formula (0) on wherein R has the same meaning as given above and (2) a silicon compound represented by the general formula wherein each R has the same meaning as given above, each of the radicals represented by the Rs attached to the Si atom in Formula (b) being the same but being ditferent from the radical represented by the R attached to the B atom in Formula (a), and Y represents a radical of the class consisting of OH and NH radicals, the boronic acid of (1) and the silicon compound of (2) being employed in a molar ratio of at least 2 moles of the latter per mole of the former; and isolating a compound represented by the first-given formula from the resulting reaction mass.

OTHER REFERENCES Wiberg et al.: Zeitschrift fiir Naturforschung, vol. 8b (October 1953), pp. 609-10. 

1. THE METHOD OF PREPARING A COMPOUND REPRESENTED BY THE GENERAL FORMULA 